Yocto Project Quick Start

Welcome!

Welcome to the Yocto Project!
The Yocto Project is an open-source collaboration project focused on embedded Linux
developers.
Among other things, the Yocto Project uses a build system based on the Poky project
to construct complete Linux images.
The Poky project, in turn, draws from and contributes back to the OpenEmbedded project.

If you don't have a system that runs Linux and you want to give the Yocto Project a test run,
you might consider using the Yocto Project Build Appliance.
The Build Appliance allows you to build and boot a custom embedded Linux image with the Yocto
Project using a non-Linux development system.
See the Yocto
Project Build Appliance for more information.

On the other hand, if you know all about open-source development, Linux development environments,
Git source repositories and the like and you just want some quick information that lets you try out
the Yocto Project on your Linux system, skip right to the
"Super User" section at the end of this quick start.

For the rest of you, this short document will give you some basic information about the environment and
let you experience it in its simplest form.
After reading this document, you will have a basic understanding of what the Yocto Project is
and how to use some of its core components.
This document steps you through a simple example showing you how to build a small image
and run it using the Quick EMUlator (QEMU emulator).

For more detailed information on the Yocto Project, you should check out these resources:

Website: The Yocto Project Website
provides the latest builds, breaking news, full development documentation, and a rich Yocto
Project Development Community into which you can tap.

FAQs: Lists commonly asked Yocto Project questions and answers.
You can find two FAQs: Yocto Project FAQ on
a wiki, and the
"FAQ" chapter in
the Yocto Project Reference Manual.

Note

Due to production processes, there could be differences between the Yocto Project
documentation bundled in a released tarball and the
Yocto Project Quick Start on
the Yocto Project website.
For the latest version of this manual, see the manual on the website.

Introducing the Yocto Project Development Environment

The Yocto Project through the OpenEmbedded build system provides an open source development
environment targeting the ARM, MIPS, PowerPC and x86 architectures for a variety of
platforms including x86-64 and emulated ones.
You can use components from the Yocto Project to design, develop, build, debug, simulate,
and test the complete software stack using Linux, the X Window System, GNOME Mobile-based
application frameworks, and Qt frameworks.

The Yocto Project Development Environment

Here are some highlights for the Yocto Project:

Provides a recent Linux kernel along with a set of system commands and libraries suitable for the embedded environment.

Makes available system components such as X11, GTK+, Qt, Clutter, and SDL
(among others) so you can create a rich user experience on devices
that have display hardware.
For devices that don't have a display or where you wish to use alternative UI
frameworks, these components need not be installed.

Creates a focused and stable core compatible with the OpenEmbedded
project with which you can easily and reliably build and develop.

Fully supports a wide range of hardware and device emulation through the QEMU
Emulator.

The Yocto Project can generate images for many kinds of devices.
However, the standard example machines target QEMU full-system emulation for x86, x86-64, ARM, MIPS,
and PPC-based architectures as well as specific hardware such as the
Intel® Desktop Board DH55TC.
Because an image developed with the Yocto Project can boot inside a QEMU emulator, the
development environment works nicely as a test platform for developing embedded software.

Another important Yocto Project feature is the Sato reference User Interface.
This optional GNOME mobile-based UI, which is intended for devices with
restricted screen sizes, sits neatly on top of a device using the
GNOME Mobile Stack and provides a well-defined user experience.
Implemented in its own layer, it makes it clear to developers how they can implement
their own user interface on top of a Linux image created with the Yocto Project.

What You Need and How You Get It

You need these things to develop in the Yocto Project environment:

A host system running a supported Linux distribution (i.e. recent releases of
Fedora, openSUSE, CentOS, and Ubuntu).
If the host system supports multiple cores and threads, you can configure the
Yocto Project build system to decrease the time needed to build images
significantly.

The right packages.

A release of the Yocto Project.

The Linux Distribution

The Yocto Project team is continually verifying more and more Linux
distributions with each release.
In general, if you have the current release minus one of the following
distributions you should have no problems.

Ubuntu

Fedora

openSUSE

CentOS

For a more detailed list of distributions that support the Yocto Project,
see the
"Supported Linux Distributions" section
in the Yocto Project Reference Manual.

Note

For notes about using the Yocto Project on a RHEL 4-based host, see the
BuildingOnRHEL4
wiki page.

The OpenEmbedded build system should be able to run on any modern distribution with Python 2.6 or 2.7.
Earlier releases of Python are known to not work and the system does not support Python 3 at this time.
This document assumes you are running one of the previously noted distributions on your Linux-based
host systems.

Note

If you attempt to use a distribution not in the above list, you may or may not have success - you
are venturing into untested territory.
Refer to
OE and Your Distro and
Required Software
for information for other distributions used with the OpenEmbedded project, which might be
a starting point for exploration.
If you go down this path, you should expect problems.
When you do, please go to Yocto Project Bugzilla
and submit a bug.
We are interested in hearing about your experience.

The Packages

Packages and package installation vary depending on your development system
and on your intent.
For example, if you want to build an image that can run
on QEMU in graphical mode (a minimal, basic build
requirement), then the number of packages is different than if you want to
build an image on a headless system or build out the Yocto Project
documentation set.
Collectively, the number of required packages is large
if you want to be able to cover all cases.

Note

In general, you need to have root access and then install the
required packages.
Thus, the commands in the following section may or may not work
depending on whether or not your Linux distribution has
sudo installed.

The next few sections list, by supported Linux Distributions, the required
packages needed to build an image that runs on QEMU in graphical mode
(e.g. essential plus graphics support).

Note

Depending on the CentOS version you are using, other requirements
and dependencies might exist.
For details, you should look at the CentOS sections on the
Poky/GettingStarted/Dependencies
wiki page.

Yocto Project Release

You can download the latest Yocto Project release by going to the
Yocto Project website
clicking "Downloads" in the navigation pane to the left to view all
available Yocto Project releases.
Be sure to scroll down and look for "Yocto Project" under the
"Type" heading in the list.
Nightly and developmental builds are also maintained at
http://autobuilder.yoctoproject.org/nightly/.
However, for this document a released version of Yocto Project is used.

You can also get the Yocto Project files you need by setting up (cloning in Git terms)
a local copy of the poky Git repository on your host development
system.
Doing so allows you to contribute back to the Yocto Project project.
For information on how to get set up using this method, see the
"Yocto
Project Release" item in the Yocto Project Development Manual.

A Quick Test Run

Now that you have your system requirements in order, you can give the Yocto Project a try.
This section presents some steps that let you do the following:

Build an image and run it in the QEMU emulator

Use a pre-built image and run it in the QEMU emulator

Building an Image

In the development environment you will need to build an image whenever you change hardware
support, add or change system libraries, or add or change services that have dependencies.

Building an Image

Use the following commands to build your image.
The OpenEmbedded build process creates an entire Linux distribution, including the toolchain,
from source.

Note

The build process using Sato currently consumes about 50GB of disk space.
To allow for variations in the build process and for future package expansion, we
recommend having at least 100GB of free disk space.

Tip

To help conserve disk space during builds, you can add the following statement
to your project's configuration file, which for this example
is poky-dylan-9.0.3/build/conf/local.conf.
Adding this statement deletes the work directory used for building a package
once the package is built.

INHERIT += "rm_work"

In the previous example, the first command retrieves the Yocto Project
release tarball from the source repositories using the
wget command.
Alternatively, you can go to the
Yocto Project website's
"Downloads" page to retrieve the tarball.

The second command extracts the files from the tarball and places
them into a directory named poky-dylan-9.0.3 in the current
directory.

The third and fourth commands change the working directory to the
Source Directory
and run the Yocto Project
oe-init-build-env
environment setup script.
Running this script defines OpenEmbedded build environment settings needed to
complete the build.
The script also creates the
Build Directory,
which is build in this case and is located in the
Source Directory.
After the script runs, your current working directory is set
to the Build Directory.
Later, when the build completes, the Build Directory contains all the files
created during the build.

Take some time to examine your local.conf file
in your project's configuration directory, which is found in the Build Directory.
The defaults in that file should work fine.
However, there are some variables of interest at which you might look.

By default, the target architecture for the build is qemux86,
which produces an image that can be used in the QEMU emulator and is targeted at an
Intel® 32-bit based architecture.
To change this default, edit the value of the MACHINE variable
in the configuration file before launching the build.

Another couple of variables of interest are the
BB_NUMBER_THREADS and the
PARALLEL_MAKE variables.
By default, these variables are commented out.
However, if you have a multi-core CPU you might want to uncomment
the lines and set both variables equal to twice the number of your
host's processor cores.
Setting these variables can significantly shorten your build time.

Another consideration before you build is the package manager used when creating
the image.
By default, the OpenEmbedded build system uses the RPM package manager.
You can control this configuration by using the
PACKAGE_CLASSES variable.
For additional package manager selection information, see the
"Packaging - package*.bbclass"
section in the Yocto Project Reference Manual.

Continue with the following command to build an OS image for the target, which is
core-image-sato in this example.
For information on the -k option use the
bitbake --help command or see the
"BitBake" section in
the Yocto Project Reference Manual.

$ bitbake -k core-image-sato

Note

BitBake requires Python 2.6 or 2.7. For more information on this requirement,
see the
FAQ in the Yocto Project Reference
Manual.

The final command runs the image:

$ runqemu qemux86

Note

Depending on the number of processors and cores, the amount or RAM, the speed of your
Internet connection and other factors, the build process could take several hours the first
time you run it.
Subsequent builds run much faster since parts of the build are cached.

Using Pre-Built Binaries and QEMU

If hardware, libraries and services are stable, you can get started by using a pre-built binary
of the filesystem image, kernel, and toolchain and run it using the QEMU emulator.
This scenario is useful for developing application software.

Using a Pre-Built Image

For this scenario, you need to do several things:

Install the appropriate stand-alone toolchain tarball.

Download the pre-built image that will boot with QEMU.
You need to be sure to get the QEMU image that matches your target machine’s
architecture (e.g. x86, ARM, etc.).

Download the filesystem image for your target machine's architecture.

Set up the environment to emulate the hardware and then start the QEMU emulator.

Installing the Toolchain

You can download a tarball installer, which includes the pre-built toolchain, the
runqemu
script, and support files from the appropriate directory under
http://downloads.yoctoproject.org/releases/yocto/yocto-1.4.3/toolchain/.
Toolchains are available for 32-bit and 64-bit development systems from the
i686 and x86-64 directories, respectively.
Each type of development system supports five target architectures.
The names of the tarball installer scripts are such that a string representing the
host system appears first in the filename and then is immediately followed by a
string representing the target architecture.

poky-eglibc-<host_system>-<arch>-toolchain-gmae-<release>.sh
Where:
<host_system> is a string representing your development system:
i686 or x86_64.
<arch> is a string representing the target architecture:
i586, x86_64, powerpc, mips, or arm.
<release> is the version of Yocto Project.

For example, the following toolchain installer is for a 64-bit development
host system and a 32-bit target architecture:

poky-eglibc-x86_64-i586-toolchain-gmae-1.4.3.sh

Toolchains are self-contained and by default are installed into /opt/poky.
However, when you run the toolchain installer, you can choose an installation directory.

The following command shows how to run the installer given a toolchain tarball
for a 64-bit development host system and a 32-bit target architecture.
You must change the permissions on the toolchain
installer script so that it is executable.

The example assumes the toolchain installer is located in ~/Downloads/.

Note

If you do not have write permissions for the directory into which you are installing
the toolchain, the toolchain installer notifies you and exits.
Be sure you have write permissions in the directory and run the installer again.

The filesystem image has two tarball forms: ext3 and
tar.
You must use the ext3 form when booting an image using the
QEMU emulator.
The tar form can be flattened out in your host development system
and used for build purposes with the Yocto Project.

Continuing with the example, the following two commands setup the emulation
environment and launch QEMU.
This example assumes the root filesystem (.ext3 file) and
the pre-built kernel image file both reside in your home directory.
The kernel and filesystem are for a 32-bit target architecture.

The environment in which QEMU launches varies depending on the filesystem image and on the
target architecture.
For example, if you source the environment for the ARM target
architecture and then boot the minimal QEMU image, the emulator comes up in a new
shell in command-line mode.
However, if you boot the SDK image, QEMU comes up with a GUI.

Note

Booting the PPC image results in QEMU launching in the same shell in
command-line mode.

Super User

This section
[1]
gives you a minimal description of how to use the Yocto Project to build images
for a BeagleBoard xM starting from scratch.
The steps were performed on a 64-bit Ubuntu 10.04 system.

Initializing the Build Environment

At this point, the mybuilds directory has been created for you
and it is now your current working directory.
If you don't provide your own directory name it defaults to build,
which is inside the Source Directory.

Configuring the local.conf File

Initializing the build environment creates a conf/local.conf configuration file
in the Build Directory.
You need to manually edit this file to specify the machine you are building and to optimize
your build time.
Here are the minimal changes to make:

A good deal that goes into a Yocto Project build is simply
downloading all of the source tarballs.
Maybe you have been working with another build system
(OpenEmbedded or Angstrom) for which you have built up a sizable
directory of source tarballs.
Or, perhaps someone else has such a directory for which you have
read access.
If so, you can save time by adding statements to your
configuration file so that the build process checks local
directories first for existing tarballs before checking the
Internet.
Here is an efficient way to set it up in your
local.conf file: